The present disclosure relates to a hydraulic control system for a vehicle, in particular for a tractor.
Tractors often include hydraulic control systems that utilize a hydraulic pump to generate a flow of hydraulic fluid for control and to operate tractor implements (e.g., front shovel, rear shovel, mowing blades, planter, etc.). The hydraulic pump is driven by an engine of the tractor.
When a load from a tractor implement is not taxing the engine, the tractor typically benefits from a shift-up, throttle-back (SUTB) condition. With a higher gear ratio of the transmission, lower engine speed can achieve a required ground speed. Slower gears, shafts and other rotating components generally provide improved fluid economy. The SUTB condition may be adequate for the tractor when the tractor is planting or carrying out another operation as it traverses across a field. The hydraulic flow needs of the pump are met by the lower engine speed and are dictated by power requirements and available pump displacement. At the end of a field row or other condition requiring additional hydraulic fluid flow, however (e.g., when a planter needs to be hydraulically raised or when a tractor implement otherwise begins to tax the engine), the SUTB condition may not provide enough pump speed at a maximum displacement to meet hydraulic needs. Current systems do not change the gear ratios of the transmission in this situation. In particular, the controls of current systems do not recognize unmet hydraulic flow needs and the available pump displacement that could satisfy those needs.